1. Field of the Invention
The present invention relates to a method for detecting an assembled state of gas sensors, particularly, a wrong assembly of the same and relates to an apparatus for detecting a wrong assembly of gas sensors. More particularly, the present invention relates to a method for detecting an assembled state of gas sensors and an apparatus for detecting an assembled state of gas sensors which are disposed in individual exhaust systems of an engine including a plurality of exhaust systems and which detect an oxygen concentration in individual exhaust systems.
2. Description of the Related Art
Conventionally, in an engine of an automobile or the like, gas sensors such as oxygen sensors, air-fuel ratio sensors and the like are disposed in the exhaust system to carry out an optimum feedback control of the air-fuel ratio. While the engine is being operated, an air-fuel ratio control is carried out in the automobile based on signals detected by the gas sensors.
In an engine, such as a V engine or a horizontally-opposed engine, which includes two, that is, left and right banks, an exhaust system is provided for each bank, and a gas sensor is disposed for each exhaust system. Even in inline engines, cylinders are sometimes grouped into front and rear banks, an exhaust system is provided for each bank, and a gas sensor is disposed for each exhaust system. In such a configuration in which gas sensors are disposed so as to correspond to respective banks as described above, the gas sensors assembled at predetermined locations are electrically connected to the engine control apparatus via the wiring harnesses. At this time, to prevent an error in connection (i.e., wrong assembly) from the left and right gas sensors to the engine control apparatus, some conventional configurations have been used which physically disable a connection between left and right opposite banks. The configuration may be one having different connector shapes for left and right or one with a harness having different lengths for the left and right. In some cases, instead of a configuration which disconnects the gas sensors left and right opposite, a wrong assembly is detected by detecting abnormality in a responsiveness diagnosis (self-diagnosis) of gas sensors or fuel feedback correction amount diagnosis when left and right gas sensors are wrongly assembled, that is, left and right opposite.
In addition, a detection apparatus is proposed for a case in which a vehicle is mounted with a master unit and at least one slave unit which are electronics components communicative with each other. For example, in the case of where the slave unit is removed from the vehicle for repairing the vehicle at a maintenance shop and is attached again to the vehicle, the detection apparatus detects that a wrong part is attached in place of the slave unit which was removed. (For example, see Japanese Patent Laid-open Publication No. 2003-11746.) In the apparatus, a Micro Processing Unit (MPU) of the slave unit and an MPU of the master unit calculate respective power supply time periods starting from when the ignition switch is turned ON to when it is turned OFF. In the case where there is a significant change between the power supply time periods for both, a warning apparatus issues a warning indicating that either the master unit or the slave unit is wrongly assembled.
However, having different connector shapes or different wiring harness lengths for the left and right gas sensors causes an increase in the number of parts, leading to an increased cost. In addition, the method for detecting a wrong assembly of gas sensors by detecting abnormality with the gas sensor responsiveness diagnosis or fuel feedback correction amount diagnosis does not enable identification of whether the abnormality is caused by a wrong assembly of the gas sensors left and right opposite or by a problem in the sensor or the engine. This requires investigation of the cause though troubleshooting, requiring a lot of man-hours.
In addition, the method shown in Patent Document 1 cannot be applied to detection of a wrong assembly of gas sensors.